Various in vivo measurement systems are known in the art. They typically include ingestible electronic capsules which collect data and which transmit the data to a receiver system. These capsules, which are moved through the digestive system by peristalsis, include “Heidelberg” capsules to measure pH, “CoreTemp” capsules to measure temperature and other capsules to measure pressure throughout the intestines. They have also been used to measure gastric residence time and intestinal passage time, which is the time it takes for food to pass through the stomach and intestines.
The intestinal capsules typically include a measuring system and a transmission system, where the transmission system transmits the measured data at radio frequencies to the receiver system. Alternate systems can store all the data within a storage device in the capsule. The data can then be read after the capsule exits the gastrointestinal (GI) tract.
In vivo camera systems are known, such one known camera system which is carried by a swallowable capsule. The in vivo video camera system captures and transmits images of the GI tract while the capsule passes through the gastro-intestinal lumen. The system includes a capsule that can pass through the entire digestive tract and operate as an autonomous video endoscope.
Prior attempts at localizing an intra-gastric and intrauterine transmitting capsule includes spatially scanning a non-ambulatory patient with a receiver. The receiver and scanning system locates the points with the highest reception and plots a track of the capsule, the assumption being that the capsule is at the location where the strongest signal is received. These attempts use a laboratory device that is non-portable and non-commercial.
Other attempts at localizing an in vivo capsule analyze the statistics of signal variation during the passage of the capsule through the GI tract. Large signal level variations are observable during the passage of the capsule through specific significant locations in the lumen and these variations are associated with specific anatomical features. This method is inherently inaccurate since the anatomically significant locations of the GI tract are not rigidly attached to a fixed frame of reference.